Geothermal energy: definition, advantages and disadvantages

The Geothermal energy (From the Greek geo, Earth, and Thermosheat; that is, “heat of the earth”) is a type of renewable energy that, as we deduce from his name, uses the internal heat of the earth as a source stored under the surface. The earth’s core is formed by an incandescent solid sphere and is composed mainly of an iron and nickel alloy that radiates heat to the outside. Thus, the deepest layers have higher temperatures and in them the water mass heating can occur that, as it ascends in a liquid or vapor state, are manifested in the form of geyser or thermal sources.

This heat is not transmitted in a linear way through all points of the planet and, in addition, it depends on the material that crosses. The most superficial area of ​​the earth’s crust, the lithosphere, transports heat by driving (by contact between the two bodies but without the transfer of matter) already measure that the depth increases, the heat is transmitted by convection (it is produced by the transfer of the heat carrier matter, usually a gas or liquid, to the receiving body).

Currently, geothermal energy is used to Heat, cooling and electric power generation.

Exist 4 types of geothermal energy depending on the water temperature when expelled:

• High temperature geothermal energybetween 150 and 400º. On the earth’s surface it becomes steam and through a turbine generates electricity.
• Geothermal average temperature energybetween 70 and 150º, exploited by small electric plants.
• Low temperature geothermal energybetween 50 and 70º, used mainly for domestic needs such as heating and, more punctually, in greenhouses or agriculture.
• Very low temperature geothermal energybetween 20 and 50º. Not being sufficient for air conditioning, geothermal heat pumps should be used both to heat and refrigerate.

Within this section we can also refer to geothermal energy from hot rock deposits, about 5-8 kilometers deep under the ground (dry deposits).

Generally, the rhythm at which these deposits are exploited is usually elevated, so areas that would take hundreds of years to recover should not be saturated.

The Geothermal depositslocations in which large concentrations of geothermal energy accumulate, they can be classified into three types:

Hot water deposits

This type of deposit can be presented in the form of sources or underground in aquifers. These first have been used for a long time as thermal baths by the Romans. Underground deposits have high temperatures but at low or medium depths, so that hot water or steam can flow naturally. However, if you want to extract it for exploitation, two or a couple of wells must be carried out to extract the water and re -introduce it once cooled to prevent the aquifer from drying out and lost as thermal deposit.

Dry deposits

These deposits do not need water to produce energy, since it is actually a type of artificial production. They are found underground at a not very high depth, and are formed by Dry rocks at high temperatures due to exposure to the inner magma. They are injected with cold water that when coming into contact with the hot rock produces water vapor, which comes under pressure due to a second drilling also in contact with the hot rock bed.

GENERES

They can be the clearest example that we all have in the head, but not for that reason they are excessively abundant, being mostly distributed between Iceland and Yellowstone National Park (USA), areas fundamentally volcanic.

These geysers are great sources of boiling thermal water capable of violent expelling steam columns and hot water. The explanation of this phenomenon is based on the contact of the waters of the subsoil with the rocks that are maintained at high temperatures inside the earth. This causes water to heat up and volatilize almost instantaneously, ascending to the surface at high speed and expelling itself as if the geyser was a siphon of water and steam.

This type of energy presents both advantages and disadvantages that should be known. Thus, among the main advantages of geothermal energy We highlight the following:

• It is a renewable resource, provided that its extraction rate is lower than the natural recharge rate.
• It is considered a “clean” energy, as it reduces the consumption of fossil fuels and other non -renewable resources.
• It barely produces waste, which largely reduces the environmental impact.
• The emission of greenhouse CO2 is much lower than that produced by combustion to obtain the same energy, so just It contributes to global warming.
• It is a saving since its costs for electricity production are low.
• Provides a lot of resources; It is believed that today it can provide more energy than all fossil fuels (oil, natural gas, coal and uranium) together.

In addition, as we have commented before, Geothermal energy also has inconvenience:

• Under development because it is an energy that is beginning to be used. In Spain it is barely exploited and extraction methods can currently be considered somewhat ordinary.
• Leaks may occur in which sulfide acid is expelled (in high doses it is lethal for man), arsenic, ammonia or other substances that can cause contamination of the terrain and nearby waters.
• The geothermal plants or central They must be installed in places where the heat of the subsoil is high.
• This energy is not transportable and should be used In situthat is, in the same place that occurs (local supply).
• They produce impact on the landscape, since the construction of the facilities to extract the heat from the underground rocks and the magma must be made in the field.
• Small are produced in areas close to geothermal plants because of abrupt cooling and breakage of the rock cortex rocks.
• Thermal contamination
• Noise pollution. In initial phases in which the drilling of wells is necessary to reach up to 115 decibels (almost the noise generated by the engine of an airplane), although once performed, its usual operation does not produce barely exterior noises (it is between 75 and the 80 decibels, the noise of a vacuum).

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